J2EE is a set of Java-based technologies used to build applications accessible over the network. Flexibility and the ability to configure, based mainly on XML files, leads to the fact that more and more errors are beyond the control of the compiler.
Older systems described the interaction between parts of the system directly in the code and as such could you checked (at least partially) in the build phase by compiler. The trend to move this kind of information outside of Java code causes, unfortunately, many configuration errors will not be caught by compiler. Those errors will be visible later, at run time.
The complexity of the J2EE architecture makes the cycle (recompilation, installation, testing in a browser) long. This significantly makes the development method “change and run” harder. What can we do to speed up the process of developing J2EE applications?
(This is a translation of an article I wrote two years ago on static verification).
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“ORA-01722: invalid number” is raised when a number was passed a query parameter, but another type (string) was expected.
The error message isn’t very helpful, is it?
Linode.com sells unmanaged VPS servers based on Xen virtualisation technology.
VPS stands for Virtual Private Server and it means one phisycal server is split into smaller parts and every “part” gains his own IP, disk space, CPU and IO resources. You are sharing server resources with other VPS-es, but have much better isolation and customisation than shared hosting supports.
Off-topic note: Besides there’s management panel for Linode you should know Linux/Unix administration very well to make use of “unmanaged VPS”. If you are not advanced administrator better stay with shared hosting or buy “managed VPS”. It will save you many headaches later. VPS (like dedicated server) is not a “piece of cake” for novice webmaster. You’ve been warned.
It’s a review written after one year use of Linode services for one of my customers, Cartalia.com.
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Próbowałem dziś zalogować się na GL i zauważyłem, że serwis nie działa tak jak powinien (częste “timeouty” w przeglądarce). Postanowiłem przyjrzeć sie bliżej działaniu serwera i założyłem monitor na niego przy użyciu site-uptime.net (interwał 15 minut, metoda: HEAD HTTP/1.0). Oto rezultat po dwóch godzinach monitorowania (ujemna wartość oznacza brak dostępności serwera):
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Aplikacja.info believes in continuous integration and frequent reases, so uses so-called stable trunk policy. That means: at any time any developer can make installation from trunk to production systems. How stable trunk can be achieved?
- any commit done to trunk is protected by set of automated tests that should run 100% clean (more critical project will use framework for a continuous build process like Cruise Control or PQM).
- “risky” tasks are done using peer code review process based on version control software
What to review?
We believe the most efficient method of reviewing code is to look at changesets (unified diffs). Then reviewer can see exact changes done by another developer to meet task criteria and codebase to review is minimized to really important parts of code (changes with some lines of context). That’s why we believe forming proper changesets is very important requirement.
Commit methods
There are mainly three methods of inserting new commits into trunk (specified in our implementation by special “target” field in bug tracker):
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